29June2017page1of3BUILDINGMASSRAPIDTRANSPORTSYSTEMS

ABOVEGROUNDORBELOWGROUND?

1. Backgroundandintroduction

TheCityofBogotáinColombiaisconsideringanewmetrosystem.Thecurrentplansindicatethistobeanelevatedmetrothatrunsthroughthecity.ACTOShasaskedITACUStoindicatetheirthoughtsonthismatter.

ArtistimpressionoftheelevatedmetroinBogotá

2. ITAWorkingGroup13report

ITA1WorkingGroup13madeanextensiveinvestigationintotheargumentsforandagainstplacingametrobelowthesurface.Thereporthasbeenattachedandalthoughitwaswrittenin2003,manyoftheargumentsinthisreportstillholdtruetoday.Theargumentswillnotberepeatedhere,pleaserefertothereportforthis.

3. TheCitiesWeNeed

In2014theWorldUrbanForumwasheldinMedellin,Colombia.Theevent,organisedbyUNHabitatwasbasedonthequestionwherearewegoingwithourcities.FromthistheWorldUrbanCampaigndevelopedthe‘CitiesWeNeed’campaign.Twopointsinthiscontextarerelevantforpoliticaldecisionmakers,policymakersandurbanplanners:

1InternationalTunnellingandUndergroundSpaceAssociation,Lausanne,Switzerland

29June2017page2of3• Theurbandevelopmentdecisionswemaketodaywillbeseenacrossthefacesofourcityscapes

forgenerationstocome(posterattheWorldUrbanForumheldinMedellinin2014);• Thecitieswewantshouldbeenginesofeconomicdevelopmentandlieatthecoreofanew

urbanerawherepeoplecanfindfreedom,innovation,prosperity,andresilience(PublicationbytheWorldUrbanCampaignin2016inpreparationfortheHabitatIIIconference).

WorldUrbanCampaignposterattheWorldUrbanForuminMedellin,Colombia.

Itisthesetwopointthatshouldbecriticalwhenitcomestodecidingonwhethertobuildthemetroelevatedatthesurfaceorbelowthesurface.

Elevatedinfrastructurehasbeenusedincitiesallovertheworld.Allovertheworldwenowseethesestructuresbeingtakendown.Theydivideneighbourhoods,thepreventfurtherdevelopment,theylowerthevalueofrealestateinthevicinity.Indeed,citiessuchasBoston,MA,UnitedStates;RiodeJaneiro,RJ,Brazil;andMadrid,Spain;haveallplacetheirroadinfrastructurebelowthesurfacetofreeupsurfacespace.Valuablesurfacespacethatwasoftenredevelopedintogreenpublicspaces.Thereasonforthisisthatcitiesnotonlyfacethechallengetobeliveableandinclusivefortheircitizens,theyneedtobeclimateproofandresilientaswell.Greenpublicspacesprovidenaturalinfiltrationofrainwater,thetreesabsorbCO2andthegreeneryreducestheurbanheatislandeffect.Oneofthechallengeswehaveisthatastheclimateischanging,ourcitiesareheatingwhichiscausinghealthproblemsforthecitizens.Introducingnewconcretestructuresintothecityonlyraisesthiseffect.

29June2017page3of3Soapartfromallotherarguments,citiesthatlooktowardthefutureandlookattheinterestoftheircitizensshouldnotbeplanninglargeconcreteinfrastructuresthatdeterioratelivingconditions,introducenewhealthhazardsandmisshapethecityscapeforyearstocome.

Theinvestmentinanundergroundtransportsystemcouldinitiallybehigher.Butitalsooffersmanyadvantages.Thesocietalbenefitsofanundergroundsystemarenotjusttherapidtransportofpeople.Thereisnodirectimpactatthesurfaceprovidingcitizenswithamajoradvantagethatleavesspacetofurtherenhancethequalitiesofthecity.

Byplacingthemetroundergroundthereisalsoanelementofflexibility.AscanbeseenfromthedevelopmentofmetrosystemsinLondon,Parisandothercities–newlinescaneasilybeintroducedandcrossunderexistinglines.Doingthisatthesurfacewouldeitherbeverydifficultorresultinastackedelevatemetrosystemthatwouldevenfurtherdestroythecityscape.

4. Inconclusion

ThequestionofwhetherthemetroinBogotáneedstobeelevatedatthesurfaceorplacedbelowthesurfaceisnotatechnicaldiscussion.Itshouldalsonotbeadiscussionaboutcost.Aboveall,itisadiscussionontheBogotáofthefutureandhowthatcityshouldlook.Iflessonsaretobelearnedfromothercitiesworldwide,itisthatelevatedinfrastructurehasalwaysintheendproventobeabadlong-terminvestment.Removingtheelevatedinfrastructurehasledtointroducinganewqualityintoareasthathadbecomederelictbecauseofthepresenceofthatinfrastructure.Bynotbuildingthesestructuresinthefirstplace,butchoosingforanalternative,thepoliticiansofthedaycouldbemakingadecisionthatwouldbeapplaudedbytheircitizensinyearstocome.

ThenewmuseumbyCalatravaonthewaterfrontofRiodeJaneiroonlycameaboutthroughtheremovaloftheelevatedPeremitralHighwayandbuildingtwonewroadtunnelstocarrythetrafficbelowthesurface.Byremovingtheelevatedhighway,thewholeareacannowberevitalisedandthecitycentreisoncemoreconnectedwiththewaterfront.